What is the process of solving systems of equations

What is the value of x in the equation 2(x-4) = 4(2x + 1)?

Aregular pan has a length that is 4/3 the width. the total area of the pan is 432in.2. what is the width of the cake pan?

Percy rides his bike 11.2 miles in 1.4 hours at a constant rate. write an equation to represent the proportional relationship between the number of hours percy rides, x,and the distance in miles, y, that he travels.